Tricky brace expansion in shell

Question

When using a POSIX shell, the following

touch {quick,man,strong}ly

expands to

touch quickly manly strongly

<

Answer 1

In bash, you can do this:

#!/bin/bash
TEST=quick,man,strong
eval echo $(echo {$TEST}ly)
#eval touch $(echo {$TEST}ly)

That last line is commented out but will touch the specified files.

Answer 2

Zsh can easily do that:

TEST=quick,man,strong
print ${(s:,:)^TEST}ly

Variable content is splitted at commas, then each element is distributed to the string around the braces:

quickly manly strongly

Answer 3

Taking inspiration from the answers above:

$ TEST=quick,man,strong
$ touch $(eval echo {$TEST}ly)

Answer 4

... There is so much wrong with using eval. What you're asking is only possible with eval, BUT what you might want is easily possible without having to resort to bash bug-central.

Use arrays! Whenever you need to keep multiple items in one datatype, you need (or, should use) an array.

TEST=(quick man strong)
touch "${TEST[@]/%/ly}"

That does exactly what you want without the thousand bugs and security issues introduced and concealed in the other suggestions here.

The way it works is:

• "${foo[@]}": Expands the array named foo by expanding each of its elements, properly quoted. Don't forget the quotes!
• ${foo/a/b}: This is a type of parameter expansion that replaces the first a in foo's expansion by a b. In this type of expansion you can use % to signify the end of the expanded value, sort of like $ in regular expressions.
• Put all that together and "${foo[@]/%/ly}" will expand each element of foo, properly quote it as a separate argument, and replace each element's end by ly.